1. The Field of the Invention
The invention relates to digital storage devices having a rotating media and more specifically to systems and methods for finitely positioning a read/write slider in such a storage device.
2. The Relevant Art
Computer systems generally utilize auxiliary storage devices onto which data can be written and from which data can be read for later use. A direct access storage device (DASD) is a common auxiliary storage device in which data is stored in known locations and accessed by reference to those locations. A hard disk drive is a type of DASD that incorporates rotating magnetic disks for storing data in magnetic form on concentric, radially spaced tracks on the disk surfaces. Transducer heads driven in a path generally perpendicular to the drive axis are used to write data to and read data from addressed locations on the disks. These transducer heads are often referred to as sliders.
Current hard disk drives also typically utilize an actuator connected to the slider by a support arm assembly. The actuator moves the slider to the desired track and maintains it over the track centerline during read or write operations. The movement of the slider to a desired track is referred to as data seeking or merely “seeking,” Maintaining the slider over the centerline of the desired track during read or write operation is referred to as track following or “tracking.”
Current hard disk drives also typically utilize an actuator connected to the slider by a support arm assembly. The actuator moves the slider to the desired track and maintains it over the track centerline during read or write operations. The movement of the slider to a desired track is referred to as data seeking or merely “seeking.” Maintaining the slider over the centerline of the desired track during read or write operation is referred to as track following or “tracking.”
The voice coil motor (VCM) typically comprises a coil movable throughout the magnetic field of a permanent magnetic stator. The application of current to the VCM causes the coil, and thus the attached head, to move in a radial fashion. In the absence of bias forces, the acceleration of the coil is proportional to the applied current. A power amplifier in response to a control input supplies this current.
In modem hard disk drive systems, the density of data tracks on the magnetic disks is increasing at a dramatic rate. Prior art control systems of the described type are experiencing difficulty in adequately positioning the slider exactly over the centerline of the track for read and write operation in such high density hard disk drives. As the track pitch of hard disk drives becomes smaller, prior art VCM systems are becoming inadequate at positioning the slider with sufficient speed and accuracy to ensure that the read/write transducer remains positioned over the centerline of the desired track during read and write processes.
Accordingly, it should be apparent that a need exists for an improved positioning device capable of finely positioning the slider of a hard disk drive such that a read/write transducer can be quickly and accurately positioned over the centerline of a DASD track in response to control signals from the DASD and positioning signals from the disk surface of the hard disk drive.